/*
* xpress-compress.c
*
- * XPRESS compression routines.
- *
- * See the comments in xpress-decompress.c about the XPRESS format.
+ * A compressor that produces output compatible with the XPRESS (Huffman
+ * version) compression format.
*/
/*
- * Copyright (C) 2012, 2013 Eric Biggers
+ * Copyright (C) 2012, 2013, 2014 Eric Biggers
*
* This file is part of wimlib, a library for working with WIM files.
*
# include "config.h"
#endif
-#include "wimlib.h"
-#include "wimlib/assert.h"
-#include "wimlib/compress.h"
+#include "wimlib/compress_common.h"
+#include "wimlib/compressor_ops.h"
+#include "wimlib/endianness.h"
#include "wimlib/error.h"
+#include "wimlib/lz_mf.h"
#include "wimlib/util.h"
#include "wimlib/xpress.h"
-#include <stdlib.h>
#include <string.h>
+#include <limits.h>
+
+#define XPRESS_CACHE_PER_POS 8
+#define XPRESS_OPTIM_ARRAY_LENGTH 4096
+
+struct xpress_compressor;
+struct xpress_item;
+struct xpress_mc_pos_data;
+
+/* Internal compression parameters */
+struct xpress_compressor_params {
+
+ /* See xpress_choose_items() */
+ u32 (*choose_items_func)(struct xpress_compressor *);
+
+ /* For near-optimal parsing only */
+ u32 num_optim_passes;
+
+ /* Match-finding algorithm and parameters */
+ enum lz_mf_algo mf_algo;
+ u32 max_search_depth;
+ u32 nice_match_length;
+};
+
+/* State of the XPRESS compressor */
+struct xpress_compressor {
+
+ /* Internal compression parameters */
+ struct xpress_compressor_params params;
+
+ /* Data currently being compressed */
+ const u8 *cur_window;
+ u32 cur_window_size;
+
+ /* Lempel-Ziv match-finder */
+ struct lz_mf *mf;
+
+ /* Optimal parsing data */
+ unsigned (*get_matches_func)(struct xpress_compressor *,
+ const struct lz_match **);
+ void (*skip_bytes_func)(struct xpress_compressor *, unsigned n);
+ struct lz_match *cached_matches;
+ struct lz_match *cache_ptr;
+ struct lz_match *cache_limit;
+ struct xpress_mc_pos_data *optimum;
+ u8 costs[XPRESS_NUM_SYMBOLS];
+
+ /* The selected sequence of matches/literals */
+ struct xpress_item *chosen_items;
+
+ /* Symbol frequency counters */
+ u32 freqs[XPRESS_NUM_SYMBOLS];
+
+ /* The current Huffman code */
+ u32 codewords[XPRESS_NUM_SYMBOLS];
+ u8 lens[XPRESS_NUM_SYMBOLS];
+};
+
+/* Intermediate XPRESS match/literal format */
+struct xpress_item {
+
+ /* Bits 0 - 8: Symbol
+ * Bits 9 - 24: Length - XPRESS_MIN_MATCH_LEN
+ * Bits 25 - 28: Number of extra offset bits
+ * Bits 29+ : Extra offset bits */
+
+ u64 data;
+};
/*
- * Writes @match, which is a match given in the intermediate representation for
- * XPRESS matches, to the output stream @ostream.
+ * Match chooser position data:
*
- * @codewords and @lens provide the Huffman code that is being used.
+ * An array of these structures is used during the near-optimal match-choosing
+ * algorithm. They correspond to consecutive positions in the window and are
+ * used to keep track of the cost to reach each position, and the match/literal
+ * choices that need to be chosen to reach that position.
*/
-static int
-xpress_write_match(struct output_bitstream *ostream, u32 match,
- const u16 codewords[], const u8 lens[])
-{
- u32 adjusted_match_len = match & 0xffff;
- u32 match_offset = match >> 16;
- u32 len_hdr = min(adjusted_match_len, 0xf);
- u32 offset_bsr = bsr32(match_offset);
- u32 sym = len_hdr | (offset_bsr << 4) | XPRESS_NUM_CHARS;
- int ret;
-
- ret = bitstream_put_bits(ostream, codewords[sym], lens[sym]);
- if (ret != 0)
- return ret;
-
- if (adjusted_match_len >= 0xf) {
- u8 byte1 = min(adjusted_match_len - 0xf, 0xff);
- ret = bitstream_put_byte(ostream, byte1);
- if (ret != 0)
- return ret;
+struct xpress_mc_pos_data {
+
+ /* The cost, in bits, of the lowest-cost path that has been found to
+ * reach this position. This can change as progressively lower cost
+ * paths are found to reach this position. */
+ u32 cost;
+#define MC_INFINITE_COST UINT32_MAX
+
+ /* The match or literal that was taken to reach this position. This can
+ * change as progressively lower cost paths are found to reach this
+ * position.
+ *
+ * This variable is divided into two bitfields.
+ *
+ * Literals:
+ * Low bits are 1, high bits are the literal.
+ *
+ * Matches:
+ * Low bits are the match length, high bits are the offset.
+ */
+ u32 mc_item_data;
+#define MC_OFFSET_SHIFT 16
+#define MC_LEN_MASK ((1 << MC_OFFSET_SHIFT) - 1)
+};
+
+
+/*
+ * Structure to keep track of the current state of sending data to the
+ * compressed output buffer.
+ *
+ * The XPRESS bitstream is encoded as a sequence of little endian 16-bit coding
+ * units interwoven with literal bytes.
+ */
+struct xpress_output_bitstream {
+
+ /* Bits that haven't yet been written to the output buffer. */
+ u32 bitbuf;
+
+ /* Number of bits currently held in @bitbuf. */
+ u32 bitcount;
+
+ /* Pointer to the start of the output buffer. */
+ u8 *start;
+
+ /* Pointer to the location in the ouput buffer at which to write the
+ * next 16 bits. */
+ u8 *next_bits;
+
+ /* Pointer to the location in the output buffer at which to write the
+ * next 16 bits, after @next_bits. */
+ u8 *next_bits2;
+
+ /* Pointer to the location in the output buffer at which to write the
+ * next literal byte. */
+ u8 *next_byte;
+
+ /* Pointer to the end of the output buffer. */
+ u8 *end;
+};
+
+/*
+ * Initialize the output bitstream.
+ *
+ * @os
+ * The output bitstream structure to initialize.
+ * @buffer
+ * The buffer to write to.
+ * @size
+ * Size of @buffer, in bytes. Must be at least 4.
+ */
+static void
+xpress_init_output(struct xpress_output_bitstream *os, void *buffer, u32 size)
+{
+ os->bitbuf = 0;
+ os->bitcount = 0;
+ os->start = buffer;
+ os->next_bits = os->start;
+ os->next_bits2 = os->start + 2;
+ os->next_byte = os->start + 4;
+ os->end = os->start + size;
+}
+
+/*
+ * Write some bits to the output bitstream.
+ *
+ * The bits are given by the low-order @num_bits bits of @bits. Higher-order
+ * bits in @bits cannot be set. At most 16 bits can be written at once.
+ *
+ * If the output buffer space is exhausted, then the bits will be ignored, and
+ * xpress_flush_output() will return 0 when it gets called.
+ */
+static inline void
+xpress_write_bits(struct xpress_output_bitstream *os,
+ const u32 bits, const unsigned int num_bits)
+{
+ /* This code is optimized for XPRESS, which never needs to write more
+ * than 16 bits at once. */
+
+ os->bitcount += num_bits;
+ os->bitbuf = (os->bitbuf << num_bits) | bits;
+
+ if (os->bitcount > 16) {
+ os->bitcount -= 16;
+ if (os->end - os->next_byte >= 2) {
+ *(le16 *)os->next_bits = cpu_to_le16(os->bitbuf >> os->bitcount);
+ os->next_bits = os->next_bits2;
+ os->next_bits2 = os->next_byte;
+ os->next_byte += 2;
+ }
+ }
+}
+
+/*
+ * Interweave a literal byte into the output bitstream.
+ */
+static inline void
+xpress_write_byte(struct xpress_output_bitstream *os, u8 byte)
+{
+ if (os->next_byte < os->end)
+ *os->next_byte++ = byte;
+}
+
+/*
+ * Flush the last coding unit to the output buffer if needed. Return the total
+ * number of bytes written to the output buffer, or 0 if an overflow occurred.
+ */
+static u32
+xpress_flush_output(struct xpress_output_bitstream *os)
+{
+ if (unlikely(os->end - os->next_byte < 2))
+ return 0;
+
+ *(le16 *)os->next_bits = cpu_to_le16(os->bitbuf << (16 - os->bitcount));
+ *(le16 *)os->next_bits2 = cpu_to_le16(0);
+
+ return os->next_byte - os->start;
+}
+
+/* Output a match or literal. */
+static inline void
+xpress_write_item(struct xpress_item item, struct xpress_output_bitstream *os,
+ const u32 codewords[], const u8 lens[])
+{
+ u64 data = item.data;
+ unsigned symbol;
+ unsigned adjusted_len;
+ unsigned num_extra_bits;
+ unsigned extra_bits;
+
+ symbol = data & 0x1FF;
+
+ xpress_write_bits(os, codewords[symbol], lens[symbol]);
+
+ if (symbol < XPRESS_NUM_CHARS) /* Literal? */
+ return;
+
+ adjusted_len = (data >> 9) & 0xFFFF;
+
+ /* If length >= 18, one extra length byte.
+ * If length >= 273, three (total) extra length bytes. */
+ if (adjusted_len >= 0xf) {
+ u8 byte1 = min(adjusted_len - 0xf, 0xff);
+ xpress_write_byte(os, byte1);
if (byte1 == 0xff) {
- ret = bitstream_put_two_bytes(ostream, adjusted_match_len);
- if (ret != 0)
- return ret;
+ xpress_write_byte(os, adjusted_len & 0xff);
+ xpress_write_byte(os, adjusted_len >> 8);
}
}
- return bitstream_put_bits(ostream,
- match_offset ^ (1 << offset_bsr), offset_bsr);
+
+ num_extra_bits = (data >> 25) & 0xF;
+ extra_bits = data >> 29;
+
+ xpress_write_bits(os, extra_bits, num_extra_bits);
}
-static int
-xpress_write_compressed_literals(struct output_bitstream *ostream,
- const u32 match_tab[],
- unsigned num_matches,
- const u16 codewords[],
- const u8 lens[])
-{
- for (unsigned i = 0; i < num_matches; i++) {
- int ret;
- u32 match = match_tab[i];
-
- if (match >= XPRESS_NUM_CHARS) /* match */
- ret = xpress_write_match(ostream, match, codewords,
- lens);
- else /* literal byte */
- ret = bitstream_put_bits(ostream, codewords[match],
- lens[match]);
- if (ret != 0)
- return ret;
+/* Output a sequence of XPRESS matches and literals. */
+static void
+xpress_write_items(struct xpress_output_bitstream *os,
+ const struct xpress_item items[], u32 num_items,
+ const u32 codewords[], const u8 lens[])
+{
+ for (u32 i = 0; i < num_items; i++)
+ xpress_write_item(items[i], os, codewords, lens);
+
+ /* End-of-data symbol (required for MS compatibility) */
+ xpress_write_bits(os, codewords[XPRESS_END_OF_DATA], lens[XPRESS_END_OF_DATA]);
+}
+
+/* Make the Huffman code for XPRESS.
+ *
+ * Takes as input c->freqs and produces as output c->lens and c->codewords. */
+static void
+xpress_make_huffman_code(struct xpress_compressor *c)
+{
+ make_canonical_huffman_code(XPRESS_NUM_SYMBOLS, XPRESS_MAX_CODEWORD_LEN,
+ c->freqs, c->lens, c->codewords);
+}
+
+/* Tally, and optionally record, the specified literal byte. */
+static inline void
+xpress_declare_literal(struct xpress_compressor *c, unsigned literal,
+ struct xpress_item **next_chosen_item)
+{
+ c->freqs[literal]++;
+
+ if (next_chosen_item) {
+ *(*next_chosen_item)++ = (struct xpress_item) {
+ .data = literal,
+ };
}
- return bitstream_put_bits(ostream, codewords[XPRESS_END_OF_DATA],
- lens[XPRESS_END_OF_DATA]);
}
-static u32
-xpress_record_literal(u8 literal, void *__freq_tab)
+/* Tally, and optionally record, the specified match. */
+static inline void
+xpress_declare_match(struct xpress_compressor *c,
+ unsigned len, unsigned offset,
+ struct xpress_item **next_chosen_item)
{
- freq_t *freq_tab = __freq_tab;
- freq_tab[literal]++;
- return literal;
+ unsigned adjusted_len = len - XPRESS_MIN_MATCH_LEN;
+ unsigned len_hdr = min(adjusted_len, 0xf);
+ unsigned offset_bsr = bsr32(offset);
+ unsigned sym = XPRESS_NUM_CHARS + ((offset_bsr << 4) | len_hdr);
+
+ c->freqs[sym]++;
+
+ if (next_chosen_item) {
+ *(*next_chosen_item)++ = (struct xpress_item) {
+ .data = (u64)sym |
+ ((u64)adjusted_len << 9) |
+ ((u64)offset_bsr << 25) |
+ ((u64)(offset ^ (1U << offset_bsr)) << 29),
+ };
+ }
}
-static u32
-xpress_record_match(unsigned match_offset, unsigned match_len,
- void *freq_tab, void *ignore)
+/* Tally, and optionally record, the specified match or literal. */
+static inline void
+xpress_declare_item(struct xpress_compressor *c, u32 mc_item_data,
+ struct xpress_item **next_chosen_item)
{
- wimlib_assert(match_len >= XPRESS_MIN_MATCH &&
- match_len <= XPRESS_MAX_MATCH);
- wimlib_assert(match_offset >= XPRESS_MIN_OFFSET &&
- match_offset <= XPRESS_MAX_OFFSET);
+ unsigned len = mc_item_data & MC_LEN_MASK;
+ unsigned offset_data = mc_item_data >> MC_OFFSET_SHIFT;
- /*
- * The intermediate representation of XPRESS matches is as follows:
- *
- * bits description
- * ---- -----------------------------------------------------------
- *
- * 16-31 match offset (XPRESS_MIN_OFFSET < x < XPRESS_MAX_OFFSET)
- *
- * 0-15 adjusted match length (0 <= x <= XPRESS_MAX_MATCH - XPRESS_MIN_MATCH)
- *
- * Literals are simply represented as themselves and can be
- * distinguished from matches by the fact that only literals will have
- * the upper three bytes completely clear. */
-
- u32 adjusted_match_len = match_len - XPRESS_MIN_MATCH;
- u32 len_hdr = min(adjusted_match_len, 0xf);
- u32 offset_bsr = bsr32(match_offset);
- u32 sym = len_hdr | (offset_bsr << 4) | XPRESS_NUM_CHARS;
- ((freq_t*)freq_tab)[sym]++;
- return adjusted_match_len | (match_offset << 16);
-}
-
-static const struct lz_params xpress_lz_params = {
- .min_match = XPRESS_MIN_MATCH,
- .max_match = XPRESS_MAX_MATCH,
- .good_match = 16,
- .nice_match = 32,
- .max_chain_len = 16,
- .max_lazy_match = 16,
- .too_far = 4096,
-};
+ if (len == 1)
+ xpress_declare_literal(c, offset_data, next_chosen_item);
+ else
+ xpress_declare_match(c, len, offset_data, next_chosen_item);
+}
-/* Documented in wimlib.h */
-WIMLIBAPI unsigned
-wimlib_xpress_compress(const void *__uncompressed_data,
- unsigned uncompressed_len, void *__compressed_data)
+static inline void
+xpress_record_item_list(struct xpress_compressor *c,
+ struct xpress_mc_pos_data *cur_optimum_ptr,
+ struct xpress_item **next_chosen_item)
{
- u8 *compressed_data = __compressed_data;
- struct output_bitstream ostream;
- u32 match_tab[uncompressed_len];
- freq_t freq_tab[XPRESS_NUM_SYMBOLS];
- u16 codewords[XPRESS_NUM_SYMBOLS];
- u8 lens[XPRESS_NUM_SYMBOLS];
+ struct xpress_mc_pos_data *end_optimum_ptr;
+ u32 saved_item;
+ u32 item;
+
+ /* The list is currently in reverse order (last item to first item).
+ * Reverse it. */
+ end_optimum_ptr = cur_optimum_ptr;
+ saved_item = cur_optimum_ptr->mc_item_data;
+ do {
+ item = saved_item;
+ cur_optimum_ptr -= item & MC_LEN_MASK;
+ saved_item = cur_optimum_ptr->mc_item_data;
+ cur_optimum_ptr->mc_item_data = item;
+ } while (cur_optimum_ptr != c->optimum);
+
+ /* Walk the list of items from beginning to end, tallying and recording
+ * each item. */
+ do {
+ xpress_declare_item(c, cur_optimum_ptr->mc_item_data, next_chosen_item);
+ cur_optimum_ptr += (cur_optimum_ptr->mc_item_data) & MC_LEN_MASK;
+ } while (cur_optimum_ptr != end_optimum_ptr);
+}
+
+static inline void
+xpress_tally_item_list(struct xpress_compressor *c,
+ struct xpress_mc_pos_data *cur_optimum_ptr)
+{
+ /* Since we're just tallying the items, we don't need to reverse the
+ * list. Processing the items in reverse order is fine. */
+ do {
+ xpress_declare_item(c, cur_optimum_ptr->mc_item_data, NULL);
+ cur_optimum_ptr -= (cur_optimum_ptr->mc_item_data & MC_LEN_MASK);
+ } while (cur_optimum_ptr != c->optimum);
+}
+
+/* Tally, and optionally (if next_chosen_item != NULL) record, in order, all
+ * items in the current list of items found by the match-chooser. */
+static void
+xpress_declare_item_list(struct xpress_compressor *c,
+ struct xpress_mc_pos_data *cur_optimum_ptr,
+ struct xpress_item **next_chosen_item)
+{
+ if (next_chosen_item)
+ xpress_record_item_list(c, cur_optimum_ptr, next_chosen_item);
+ else
+ xpress_tally_item_list(c, cur_optimum_ptr);
+}
+
+static unsigned
+xpress_get_matches_fillcache(struct xpress_compressor *c,
+ const struct lz_match **matches_ret)
+{
+ struct lz_match *cache_ptr;
+ struct lz_match *matches;
unsigned num_matches;
- unsigned compressed_len;
+
+ cache_ptr = c->cache_ptr;
+ matches = cache_ptr + 1;
+ if (likely(cache_ptr <= c->cache_limit)) {
+ num_matches = lz_mf_get_matches(c->mf, matches);
+ cache_ptr->len = num_matches;
+ c->cache_ptr = matches + num_matches;
+ } else {
+ num_matches = 0;
+ }
+ *matches_ret = matches;
+ return num_matches;
+}
+
+static unsigned
+xpress_get_matches_usecache(struct xpress_compressor *c,
+ const struct lz_match **matches_ret)
+{
+ struct lz_match *cache_ptr;
+ struct lz_match *matches;
+ unsigned num_matches;
+
+ cache_ptr = c->cache_ptr;
+ matches = cache_ptr + 1;
+ if (cache_ptr <= c->cache_limit) {
+ num_matches = cache_ptr->len;
+ c->cache_ptr = matches + num_matches;
+ } else {
+ num_matches = 0;
+ }
+ *matches_ret = matches;
+ return num_matches;
+}
+
+static unsigned
+xpress_get_matches_usecache_nocheck(struct xpress_compressor *c,
+ const struct lz_match **matches_ret)
+{
+ struct lz_match *cache_ptr;
+ struct lz_match *matches;
+ unsigned num_matches;
+
+ cache_ptr = c->cache_ptr;
+ matches = cache_ptr + 1;
+ num_matches = cache_ptr->len;
+ c->cache_ptr = matches + num_matches;
+ *matches_ret = matches;
+ return num_matches;
+}
+
+static unsigned
+xpress_get_matches_noncaching(struct xpress_compressor *c,
+ const struct lz_match **matches_ret)
+{
+ *matches_ret = c->cached_matches;
+ return lz_mf_get_matches(c->mf, c->cached_matches);
+}
+
+/*
+ * Find matches at the next position in the window.
+ *
+ * This uses a wrapper function around the underlying match-finder.
+ *
+ * Returns the number of matches found and sets *matches_ret to point to the
+ * matches array. The matches will be sorted by strictly increasing length and
+ * offset.
+ */
+static inline unsigned
+xpress_get_matches(struct xpress_compressor *c,
+ const struct lz_match **matches_ret)
+{
+ return (*c->get_matches_func)(c, matches_ret);
+}
+
+static void
+xpress_skip_bytes_fillcache(struct xpress_compressor *c, unsigned n)
+{
+ struct lz_match *cache_ptr;
+
+ cache_ptr = c->cache_ptr;
+ lz_mf_skip_positions(c->mf, n);
+ if (cache_ptr <= c->cache_limit) {
+ do {
+ cache_ptr->len = 0;
+ cache_ptr += 1;
+ } while (--n && likely(cache_ptr <= c->cache_limit));
+ }
+ c->cache_ptr = cache_ptr;
+}
+
+static void
+xpress_skip_bytes_usecache(struct xpress_compressor *c, unsigned n)
+{
+ struct lz_match *cache_ptr;
+
+ cache_ptr = c->cache_ptr;
+ if (likely(cache_ptr <= c->cache_limit)) {
+ do {
+ cache_ptr += 1 + cache_ptr->len;
+ } while (--n && likely(cache_ptr <= c->cache_limit));
+ }
+ c->cache_ptr = cache_ptr;
+}
+
+static void
+xpress_skip_bytes_usecache_nocheck(struct xpress_compressor *c, unsigned n)
+{
+ struct lz_match *cache_ptr;
+
+ cache_ptr = c->cache_ptr;
+ do {
+ cache_ptr += 1 + cache_ptr->len;
+ } while (--n);
+ c->cache_ptr = cache_ptr;
+}
+
+static void
+xpress_skip_bytes_noncaching(struct xpress_compressor *c, unsigned n)
+{
+ lz_mf_skip_positions(c->mf, n);
+}
+
+/*
+ * Skip the specified number of positions in the window (don't search for
+ * matches at them).
+ *
+ * This uses a wrapper function around the underlying match-finder.
+ */
+static inline void
+xpress_skip_bytes(struct xpress_compressor *c, unsigned n)
+{
+ return (*c->skip_bytes_func)(c, n);
+}
+
+/* Set default XPRESS Huffman symbol costs to bootstrap the iterative
+ * optimization algorithm. */
+static void
+xpress_set_default_costs(u8 costs[])
+{
unsigned i;
- int ret;
- u8 uncompressed_data[uncompressed_len + 8];
- memcpy(uncompressed_data, __uncompressed_data, uncompressed_len);
- memset(uncompressed_data + uncompressed_len, 0, 8);
+ /* Literal symbols */
+ for (i = 0; i < XPRESS_NUM_CHARS; i++)
+ costs[i] = 8;
- wimlib_assert(uncompressed_len <= 32768);
+ /* Match symbols */
+ for (; i < XPRESS_NUM_SYMBOLS; i++)
+ costs[i] = 10;
+}
- /* XPRESS requires 256 bytes of overhead for the Huffman tables, so it's
- * impossible cannot compress 256 bytes or less of data to less than the
- * input size.
- *
- * +1 to take into account that the buffer for compressed data is 1 byte
- * smaller than the buffer for uncompressed data.
- *
- * +4 to take into account that init_output_bitstream() requires at
- * least 4 bytes of data. */
- if (uncompressed_len < XPRESS_NUM_SYMBOLS / 2 + 1 + 4)
- return 0;
+/* Copy the Huffman codeword lengths array @lens to the Huffman symbol costs
+ * array @costs, but also assign a default cost to each 0-length (unused)
+ * codeword. */
+static void
+xpress_set_costs(u8 costs[], const u8 lens[])
+{
+ for (unsigned i = 0; i < XPRESS_NUM_SYMBOLS; i++)
+ costs[i] = lens[i] ? lens[i] : XPRESS_MAX_CODEWORD_LEN;
+}
- ZERO_ARRAY(freq_tab);
- num_matches = lz_analyze_block(uncompressed_data, uncompressed_len,
- match_tab, xpress_record_match,
- xpress_record_literal, freq_tab,
- NULL, freq_tab,
- &xpress_lz_params);
+/*
+ * Consider coding each match in @matches.
+ *
+ * @matches must be sorted by strictly increasing length and strictly
+ * increasing offset. This is guaranteed by the match-finder.
+ *
+ * We consider each length from the minimum (2) to the longest
+ * (matches[num_matches - 1].len). For each length, we consider only
+ * the smallest offset for which that length is available. Although
+ * this is not guaranteed to be optimal due to the possibility of a
+ * larger offset costing less than a smaller offset to code, this is a
+ * very useful heuristic.
+ */
+static inline void
+xpress_consider_matches(struct xpress_compressor *c,
+ struct xpress_mc_pos_data *cur_optimum_ptr,
+ const struct lz_match matches[],
+ unsigned num_matches)
+{
+ unsigned i = 0;
+ unsigned len = XPRESS_MIN_MATCH_LEN;
+ u32 cost;
+ u32 position_cost;
+ unsigned offset;
+ unsigned offset_bsr;
+ unsigned adjusted_len;
+ unsigned len_hdr;
+ unsigned sym;
- freq_tab[XPRESS_END_OF_DATA]++;
+ if (matches[num_matches - 1].len < 0xf + XPRESS_MIN_MATCH_LEN) {
+ /* All lengths are small. Optimize accordingly. */
+ do {
+ offset = matches[i].offset;
+ offset_bsr = bsr32(offset);
+ len_hdr = len - XPRESS_MIN_MATCH_LEN;
+ sym = XPRESS_NUM_CHARS + ((offset_bsr << 4) | len_hdr);
- make_canonical_huffman_code(XPRESS_NUM_SYMBOLS, XPRESS_MAX_CODEWORD_LEN,
- freq_tab, lens, codewords);
+ position_cost = cur_optimum_ptr->cost + offset_bsr;
+ do {
+ cost = position_cost + c->costs[sym];
+ if (cost < (cur_optimum_ptr + len)->cost) {
+ (cur_optimum_ptr + len)->cost = cost;
+ (cur_optimum_ptr + len)->mc_item_data =
+ (offset << MC_OFFSET_SHIFT) | len;
+ }
+ sym++;
+ } while (++len <= matches[i].len);
+ } while (++i != num_matches);
+ } else {
+ /* Some lengths are big. */
+ do {
+ offset = matches[i].offset;
+ offset_bsr = bsr32(offset);
+ position_cost = cur_optimum_ptr->cost + offset_bsr;
+ do {
+ adjusted_len = len - XPRESS_MIN_MATCH_LEN;
+ len_hdr = min(adjusted_len, 0xf);
+ sym = XPRESS_NUM_CHARS + ((offset_bsr << 4) | len_hdr);
- /* IMPORTANT NOTE:
- *
- * It's tempting to output the 512 Huffman codeword lengths using the
- * bitstream_put_bits() function. However, this is NOT correct because
- * bitstream_put_bits() will output 2 bytes at a time in little-endian
- * order, which is the order that is needed for the compressed literals.
- * However, the bytes in the lengths table are in order, so they need to
- * be written one at a time without using bitstream_put_bits().
- *
- * Because of this, init_output_bitstream() is not called until after
- * the lengths table is output.
- */
- for (i = 0; i < XPRESS_NUM_SYMBOLS; i += 2)
- *compressed_data++ = (lens[i] & 0xf) | (lens[i + 1] << 4);
+ cost = position_cost + c->costs[sym];
+ if (adjusted_len >= 0xf) {
+ cost += 8;
+ if (adjusted_len - 0xf >= 0xff)
+ cost += 16;
+ }
- init_output_bitstream(&ostream, compressed_data,
- uncompressed_len - XPRESS_NUM_SYMBOLS / 2 - 1);
+ if (cost < (cur_optimum_ptr + len)->cost) {
+ (cur_optimum_ptr + len)->cost = cost;
+ (cur_optimum_ptr + len)->mc_item_data =
+ (offset << MC_OFFSET_SHIFT) | len;
+ }
+ } while (++len <= matches[i].len);
+ } while (++i != num_matches);
+ }
+}
- ret = xpress_write_compressed_literals(&ostream, match_tab,
- num_matches, codewords, lens);
- if (ret)
- return 0;
+/*
+ * The main near-optimal parsing routine.
+ *
+ * Briefly, the algorithm does an approximate minimum-cost path search to find a
+ * "near-optimal" sequence of matches and literals to output, based on the
+ * current cost model. The algorithm steps forward, position by position (byte
+ * by byte), and updates the minimum cost path to reach each later position that
+ * can be reached using a match or literal from the current position. This is
+ * essentially Dijkstra's algorithm in disguise: the graph nodes are positions,
+ * the graph edges are possible matches/literals to code, and the cost of each
+ * edge is the estimated number of bits that will be required to output the
+ * corresponding match or literal. But one difference is that we actually
+ * compute the lowest-cost path in pieces, where each piece is terminated when
+ * there are no choices to be made.
+ *
+ * If next_chosen_item != NULL, then all items chosen will be recorded (saved in
+ * the chosen_items array). Otherwise, all items chosen will only be tallied
+ * (symbol frequencies tallied in c->freqs).
+ */
+static void
+xpress_optim_pass(struct xpress_compressor *c,
+ struct xpress_item **next_chosen_item)
+{
+ const u8 *window_end;
+ const u8 *window_ptr;
+ struct xpress_mc_pos_data *cur_optimum_ptr;
+ struct xpress_mc_pos_data *end_optimum_ptr;
+ const struct lz_match *matches;
+ unsigned num_matches;
+ unsigned longest_len;
+ unsigned literal;
+ u32 cost;
- /* Flush any bits that are buffered. */
- ret = flush_output_bitstream(&ostream);
- if (ret)
- return 0;
+ window_ptr = c->cur_window;
+ window_end = &c->cur_window[c->cur_window_size];
+
+begin:
+ /* Start building a new list of items, which will correspond to the next
+ * piece of the overall minimum-cost path. */
+
+ if (window_ptr == window_end)
+ return;
+
+ cur_optimum_ptr = c->optimum;
+ cur_optimum_ptr->cost = 0;
+ end_optimum_ptr = cur_optimum_ptr;
+
+ /* The following loop runs once for each per byte in the window, except
+ * in a couple shortcut cases. */
+ for (;;) {
+
+ /* Find matches with the current position. */
+ num_matches = xpress_get_matches(c, &matches);
+
+ if (num_matches) {
+
+ longest_len = matches[num_matches - 1].len;
+
+ /* If there's a very long match, choose it immediately.
+ */
+ if (longest_len >= c->params.nice_match_length) {
+
+ xpress_skip_bytes(c, longest_len - 1);
+ window_ptr += longest_len;
+
+ if (cur_optimum_ptr != c->optimum)
+ xpress_declare_item_list(c, cur_optimum_ptr,
+ next_chosen_item);
+
+ xpress_declare_match(c, longest_len,
+ matches[num_matches - 1].offset,
+ next_chosen_item);
+ goto begin;
+ }
+
+ /* If reaching any positions for the first time,
+ * initialize their costs to "infinity". */
+ while (end_optimum_ptr < cur_optimum_ptr + longest_len)
+ (++end_optimum_ptr)->cost = MC_INFINITE_COST;
+
+ /* Consider coding a match. */
+ xpress_consider_matches(c, cur_optimum_ptr,
+ matches, num_matches);
+ } else {
+ /* No matches found. The only choice at this position
+ * is to code a literal. */
+
+ if (end_optimum_ptr == cur_optimum_ptr) {
+ #if 1
+ /* Optimization for single literals. */
+ if (likely(cur_optimum_ptr == c->optimum)) {
+ xpress_declare_literal(c, *window_ptr++,
+ next_chosen_item);
+ if (window_ptr == window_end)
+ return;
+ continue;
+ }
+ #endif
+ (++end_optimum_ptr)->cost = MC_INFINITE_COST;
+ }
+ }
+
+ /* Consider coding a literal. */
+ literal = *window_ptr++;
+ cost = cur_optimum_ptr->cost + c->costs[literal];
+ if (cost < (cur_optimum_ptr + 1)->cost) {
+ (cur_optimum_ptr + 1)->cost = cost;
+ (cur_optimum_ptr + 1)->mc_item_data =
+ ((u32)literal << MC_OFFSET_SHIFT) | 1;
+ }
+
+ /* Advance to the next position. */
+ cur_optimum_ptr++;
+
+ /*
+ * This loop will terminate when either of the following
+ * conditions is true:
+ *
+ * (1) cur_optimum_ptr == end_optimum_ptr
+ *
+ * There are no paths that extend beyond the current
+ * position. In this case, any path to a later position
+ * must pass through the current position, so we can go
+ * ahead and choose the list of items that led to this
+ * position.
+ *
+ * (2) cur_optimum_ptr == &c->optimum[XPRESS_OPTIM_ARRAY_LENGTH]
+ *
+ * This bounds the number of times the algorithm can step
+ * forward before it is guaranteed to start choosing items.
+ * This limits the memory usage. But
+ * XPRESS_OPTIM_ARRAY_LENGTH is high enough that on most
+ * inputs this limit is never reached.
+ *
+ * Note: no check for end-of-block is needed because
+ * end-of-block will trigger condition (1).
+ */
+ if (cur_optimum_ptr == end_optimum_ptr ||
+ cur_optimum_ptr == &c->optimum[XPRESS_OPTIM_ARRAY_LENGTH])
+ break;
+ }
- /* Assert that there are no output bytes between the ostream.output
- * pointer and the ostream.next_bit_output pointer. This can only
- * happen if bytes had been written at the ostream.output pointer before
- * the last bit word was written to the stream. But, this does not
- * occur since xpress_write_match() always finishes by writing some bits
- * (a Huffman symbol), and the bitstream was just flushed. */
- wimlib_assert(ostream.output - ostream.next_bit_output == 2);
-
- /* The length of the compressed data is supposed to be the value of the
- * ostream.output pointer before flushing, which is now the
- * output.next_bit_output pointer after flushing.
+ /* Choose the current list of items that constitute the minimum-cost
+ * path to the current position. */
+ xpress_declare_item_list(c, cur_optimum_ptr, next_chosen_item);
+ goto begin;
+}
+
+/* Near-optimal parsing */
+static u32
+xpress_choose_near_optimal_items(struct xpress_compressor *c)
+{
+ u32 num_passes_remaining = c->params.num_optim_passes;
+ struct xpress_item *next_chosen_item;
+ struct xpress_item **next_chosen_item_ptr;
+
+ /* Choose appropriate match-finder wrapper functions. */
+ if (c->params.num_optim_passes > 1) {
+ c->get_matches_func = xpress_get_matches_fillcache;
+ c->skip_bytes_func = xpress_skip_bytes_fillcache;
+ } else {
+ c->get_matches_func = xpress_get_matches_noncaching;
+ c->skip_bytes_func = xpress_skip_bytes_noncaching;
+ }
+
+ /* The first optimization pass will use a default cost model. Each
+ * additional optimization pass will use a cost model computed from the
+ * previous pass.
*
- * There will be an extra 2 bytes at the ostream.bit_output pointer,
- * which is zeroed out. (These 2 bytes may be either the last bytes in
- * the compressed data, in which case they are actually unnecessary, or
- * they may precede a number of bytes embedded into the bitstream.) */
- if (ostream.bit_output >
- (const u8*)__compressed_data + uncompressed_len - 3)
- return 0;
- *(u16*)ostream.bit_output = cpu_to_le16(0);
- compressed_len = ostream.next_bit_output - (const u8*)__compressed_data;
-
- wimlib_assert(compressed_len <= uncompressed_len - 1);
-
-#ifdef ENABLE_VERIFY_COMPRESSION
- /* Verify that we really get the same thing back when decompressing. */
- {
- u8 buf[uncompressed_len];
- ret = wimlib_xpress_decompress(__compressed_data, compressed_len,
- buf, uncompressed_len);
- if (ret) {
- ERROR("xpress_compress(): Failed to decompress data we "
- "compressed");
- abort();
+ * To improve performance, we only generate the array containing the
+ * matches and literals in intermediate form on the final pass. For
+ * earlier passes, tallying symbol frequencies is sufficient. */
+ xpress_set_default_costs(c->costs);
+
+ next_chosen_item_ptr = NULL;
+ do {
+ /* Reset the match-finder wrapper. */
+ c->cache_ptr = c->cached_matches;
+
+ if (num_passes_remaining == 1) {
+ /* Last pass: actually generate the items. */
+ next_chosen_item = c->chosen_items;
+ next_chosen_item_ptr = &next_chosen_item;
}
- for (i = 0; i < uncompressed_len; i++) {
- if (buf[i] != uncompressed_data[i]) {
- ERROR("xpress_compress(): Data we compressed didn't "
- "decompress to the original data (difference at "
- "byte %u of %u)", i + 1, uncompressed_len);
- abort();
+
+ /* Choose the items. */
+ xpress_optim_pass(c, next_chosen_item_ptr);
+
+ if (num_passes_remaining > 1) {
+ /* This isn't the last pass. */
+
+ /* Make the Huffman code from the symbol frequencies. */
+ c->freqs[XPRESS_END_OF_DATA]++;
+ xpress_make_huffman_code(c);
+
+ /* Reset symbol frequencies. */
+ memset(c->freqs, 0, sizeof(c->freqs));
+
+ /* Update symbol costs. */
+ xpress_set_costs(c->costs, c->lens);
+
+ /* Choose appopriate match-finder wrapper functions. */
+ if (c->cache_ptr <= c->cache_limit) {
+ c->get_matches_func = xpress_get_matches_usecache_nocheck;
+ c->skip_bytes_func = xpress_skip_bytes_usecache_nocheck;
+ } else {
+ c->get_matches_func = xpress_get_matches_usecache;
+ c->skip_bytes_func = xpress_skip_bytes_usecache;
}
}
+ } while (--num_passes_remaining);
+
+ /* Return the number of items chosen. */
+ return next_chosen_item - c->chosen_items;
+}
+
+/* Lazy parsing */
+static u32
+xpress_choose_lazy_items(struct xpress_compressor *c)
+{
+ const u8 *window_ptr = c->cur_window;
+ const u8 *window_end = &c->cur_window[c->cur_window_size];
+ struct xpress_item *next_chosen_item = c->chosen_items;
+ u32 len_3_too_far;
+ struct lz_mf *mf = c->mf;
+ struct lz_match *matches = c->cached_matches;
+ unsigned num_matches;
+ struct lz_match prev_match;
+
+ if (c->cur_window_size <= 8192)
+ len_3_too_far = 2048;
+ else
+ len_3_too_far = 4096;
+
+ do {
+ /* Don't have match at previous position */
+
+ num_matches = lz_mf_get_matches(mf, matches);
+ window_ptr++;
+
+ if (num_matches == 0 ||
+ (matches[num_matches - 1].len == 3 &&
+ matches[num_matches - 1].offset >= len_3_too_far))
+ {
+ /* No matches found => output literal */
+ xpress_declare_literal(c, *(window_ptr - 1),
+ &next_chosen_item);
+ continue;
+ }
+
+ prev_match = matches[num_matches - 1];
+
+ have_prev_match:
+ /* Have match at previous position */
+
+ if (prev_match.len >= c->params.nice_match_length) {
+ /* Very long match found => output immediately */
+ xpress_declare_match(c, prev_match.len,
+ prev_match.offset,
+ &next_chosen_item);
+ lz_mf_skip_positions(mf, prev_match.len - 1);
+ window_ptr += prev_match.len - 1;
+ continue;
+ }
+
+ num_matches = lz_mf_get_matches(mf, matches);
+ window_ptr++;
+
+ if (num_matches == 0 ||
+ (matches[num_matches - 1].len <= prev_match.len))
+ {
+ /* Next match is not longer => output previous match */
+ xpress_declare_match(c, prev_match.len,
+ prev_match.offset,
+ &next_chosen_item);
+ lz_mf_skip_positions(mf, prev_match.len - 2);
+ window_ptr += prev_match.len - 2;
+ continue;
+ }
+
+ /* Next match is longer => output literal */
+
+ xpress_declare_literal(c, *(window_ptr - 2), &next_chosen_item);
+
+ prev_match = matches[num_matches - 1];
+
+ goto have_prev_match;
+
+ } while (window_ptr != window_end);
+
+ return next_chosen_item - c->chosen_items;
+}
+
+/* Greedy parsing */
+static u32
+xpress_choose_greedy_items(struct xpress_compressor *c)
+{
+ const u8 *window_ptr = c->cur_window;
+ const u8 *window_end = &c->cur_window[c->cur_window_size];
+ struct xpress_item *next_chosen_item = c->chosen_items;
+ u32 len_3_too_far;
+ struct lz_mf *mf = c->mf;
+ struct lz_match *matches = c->cached_matches;
+ unsigned num_matches;
+
+ if (c->cur_window_size <= 8192)
+ len_3_too_far = 2048;
+ else
+ len_3_too_far = 4096;
+
+ do {
+ /* Get longest match at the current position. */
+ num_matches = lz_mf_get_matches(mf, matches);
+
+ if (num_matches == 0 ||
+ (matches[num_matches - 1].len == 3 &&
+ matches[num_matches - 1].offset >= len_3_too_far))
+ {
+ /* No match, or length 3 match with large offset.
+ * Choose a literal. */
+ xpress_declare_literal(c, *window_ptr, &next_chosen_item);
+ window_ptr += 1;
+ } else {
+ /* Match found. Choose it. */
+ unsigned len = matches[num_matches - 1].len;
+ unsigned offset = matches[num_matches - 1].offset;
+
+ xpress_declare_match(c, len, offset, &next_chosen_item);
+ lz_mf_skip_positions(mf, len - 1);
+ window_ptr += len;
+ }
+ } while (window_ptr != window_end);
+
+ return next_chosen_item - c->chosen_items;
+}
+
+/* Literals-only parsing */
+static u32
+xpress_choose_literals(struct xpress_compressor *c)
+{
+ const u8 *window_ptr = c->cur_window;
+ const u8 *window_end = &c->cur_window[c->cur_window_size];
+ struct xpress_item *next_chosen_item = c->chosen_items;
+
+ do {
+ xpress_declare_literal(c, *window_ptr++, &next_chosen_item);
+ } while (window_ptr != window_end);
+
+ return next_chosen_item - c->chosen_items;
+}
+
+/*
+ * 'choose_items_func' is provided a data buffer c->cur_window of length
+ * c->cur_window_size bytes. This data buffer will have already been loaded
+ * into the match-finder c->mf. 'choose_items_func' must choose the
+ * match/literal sequence to output to represent this data buffer. The
+ * intermediate representation of this match/literal sequence must be recorded
+ * in c->chosen_items, and the Huffman symbols used must be tallied in c->freqs.
+ * The return value must be the number of items written to c->chosen_items.
+ */
+static u32
+xpress_choose_items(struct xpress_compressor *c)
+{
+ return (*c->params.choose_items_func)(c);
+}
+
+/* Set internal compression parameters for the specified compression level and
+ * maximum window size. */
+static void
+xpress_build_params(unsigned int compression_level, u32 max_window_size,
+ struct xpress_compressor_params *xpress_params)
+{
+ memset(xpress_params, 0, sizeof(*xpress_params));
+ xpress_params->num_optim_passes = 1;
+
+ if (compression_level == 1) {
+
+ /* Literal-only parsing */
+ xpress_params->choose_items_func = xpress_choose_literals;
+ xpress_params->mf_algo = LZ_MF_NULL;
+
+ } else if (compression_level < 30) {
+
+ /* Greedy parsing */
+ xpress_params->choose_items_func = xpress_choose_greedy_items;
+ xpress_params->mf_algo = LZ_MF_HASH_CHAINS;
+ xpress_params->nice_match_length = compression_level;
+ xpress_params->max_search_depth = compression_level / 2;
+
+ } else if (compression_level < 60) {
+
+ /* Lazy parsing */
+ xpress_params->choose_items_func = xpress_choose_lazy_items;
+ xpress_params->mf_algo = LZ_MF_HASH_CHAINS;
+ xpress_params->nice_match_length = compression_level;
+ xpress_params->max_search_depth = compression_level / 2;
+
+ } else {
+
+ /* Near-optimal parsing */
+ xpress_params->choose_items_func = xpress_choose_near_optimal_items;
+ if (max_window_size >= 16384)
+ xpress_params->mf_algo = LZ_MF_BINARY_TREES;
+ else
+ xpress_params->mf_algo = LZ_MF_HASH_CHAINS;
+ xpress_params->num_optim_passes = compression_level / 40;
+ xpress_params->nice_match_length = min(compression_level / 2,
+ XPRESS_MAX_MATCH_LEN);
+ xpress_params->max_search_depth = min(compression_level,
+ XPRESS_MAX_MATCH_LEN);
}
-#endif
- return compressed_len;
}
+
+/* Given the internal compression parameters and maximum window size, build the
+ * Lempel-Ziv match-finder parameters. */
+static void
+xpress_build_mf_params(const struct xpress_compressor_params *xpress_params,
+ u32 max_window_size, struct lz_mf_params *mf_params)
+{
+ memset(mf_params, 0, sizeof(*mf_params));
+
+ mf_params->algorithm = xpress_params->mf_algo;
+ mf_params->max_window_size = max_window_size;
+ mf_params->min_match_len = XPRESS_MIN_MATCH_LEN;
+ mf_params->max_match_len = XPRESS_MAX_MATCH_LEN;
+ mf_params->max_search_depth = xpress_params->max_search_depth;
+ mf_params->nice_match_len = xpress_params->nice_match_length;
+}
+
+static void
+xpress_free_compressor(void *_c);
+
+static u64
+xpress_get_needed_memory(size_t max_window_size, unsigned int compression_level)
+{
+ u64 size = 0;
+ struct xpress_compressor_params params;
+
+ if (max_window_size > XPRESS_MAX_OFFSET + 1)
+ return 0;
+
+ xpress_build_params(compression_level, max_window_size, ¶ms);
+
+ size += sizeof(struct xpress_compressor);
+
+ /* mf */
+ size += lz_mf_get_needed_memory(params.mf_algo, max_window_size);
+
+ /* optimum */
+ if (params.choose_items_func == xpress_choose_near_optimal_items) {
+ size += (XPRESS_OPTIM_ARRAY_LENGTH + params.nice_match_length) *
+ sizeof(struct xpress_mc_pos_data);
+ }
+
+ /* cached_matches */
+ if (params.num_optim_passes > 1) {
+ size_t cache_len = max(max_window_size * XPRESS_CACHE_PER_POS,
+ params.max_search_depth + 1);
+ size += cache_len * sizeof(struct lz_match);
+ } else {
+ size += params.max_search_depth * sizeof(struct lz_match);
+ }
+
+ /* chosen_items */
+ size += max_window_size * sizeof(struct xpress_item);
+
+ return size;
+}
+
+static int
+xpress_create_compressor(size_t max_window_size, unsigned int compression_level,
+ void **c_ret)
+{
+ struct xpress_compressor *c;
+ struct xpress_compressor_params params;
+ struct lz_mf_params mf_params;
+
+ if (max_window_size > XPRESS_MAX_OFFSET + 1)
+ return WIMLIB_ERR_INVALID_PARAM;
+
+ xpress_build_params(compression_level, max_window_size, ¶ms);
+ xpress_build_mf_params(¶ms, max_window_size, &mf_params);
+
+ c = CALLOC(1, sizeof(struct xpress_compressor));
+ if (!c)
+ goto oom;
+
+ c->params = params;
+
+ c->mf = lz_mf_alloc(&mf_params);
+ if (!c->mf)
+ goto oom;
+
+ if (params.choose_items_func == xpress_choose_near_optimal_items) {
+ c->optimum = MALLOC((XPRESS_OPTIM_ARRAY_LENGTH +
+ params.nice_match_length) *
+ sizeof(struct xpress_mc_pos_data));
+ if (!c->optimum)
+ goto oom;
+ }
+
+ if (params.num_optim_passes > 1) {
+ size_t cache_len = max(max_window_size * XPRESS_CACHE_PER_POS,
+ params.max_search_depth + 1);
+ c->cached_matches = MALLOC(cache_len * sizeof(struct lz_match));
+ if (!c->cached_matches)
+ goto oom;
+ c->cache_limit = c->cached_matches + cache_len -
+ (params.max_search_depth + 1);
+ } else {
+ c->cached_matches = MALLOC(params.max_search_depth *
+ sizeof(struct lz_match));
+ if (!c->cached_matches)
+ goto oom;
+ }
+
+ c->chosen_items = MALLOC(max_window_size * sizeof(struct xpress_item));
+ if (!c->chosen_items)
+ goto oom;
+
+ *c_ret = c;
+ return 0;
+
+oom:
+ xpress_free_compressor(c);
+ return WIMLIB_ERR_NOMEM;
+}
+
+static size_t
+xpress_compress(const void *uncompressed_data, size_t uncompressed_size,
+ void *compressed_data, size_t compressed_size_avail, void *_c)
+{
+ struct xpress_compressor *c = _c;
+ u32 num_chosen_items;
+ u8 *cptr;
+ struct xpress_output_bitstream os;
+ u32 compressed_size;
+
+ /* XPRESS requires 256 bytes of overhead for the Huffman code, so it's
+ * impossible to compress 256 bytes or less of data to less than the
+ * input size. */
+ if (compressed_size_avail < XPRESS_NUM_SYMBOLS / 2 + 50)
+ return 0;
+
+ /* Determine match/literal sequence. */
+ c->cur_window = uncompressed_data;
+ c->cur_window_size = uncompressed_size;
+ lz_mf_load_window(c->mf, c->cur_window, c->cur_window_size);
+ memset(c->freqs, 0, sizeof(c->freqs));
+ num_chosen_items = xpress_choose_items(c);
+ c->freqs[XPRESS_END_OF_DATA]++;
+ xpress_make_huffman_code(c);
+
+ /* Output the Huffman code as a series of 512 4-bit lengths. */
+ cptr = compressed_data;
+ for (unsigned i = 0; i < XPRESS_NUM_SYMBOLS; i += 2)
+ *cptr++ = (c->lens[i] & 0xf) | (c->lens[i + 1] << 4);
+
+ /* Output the encoded matches/literals. */
+ xpress_init_output(&os, cptr,
+ compressed_size_avail - XPRESS_NUM_SYMBOLS / 2);
+ xpress_write_items(&os, c->chosen_items, num_chosen_items,
+ c->codewords, c->lens);
+
+ /* Flush any pending data and get the length of the compressed data. */
+ compressed_size = xpress_flush_output(&os);
+ if (compressed_size == 0)
+ return 0;
+
+ /* Return the length of the compressed data. */
+ return compressed_size + XPRESS_NUM_SYMBOLS / 2;
+}
+
+static void
+xpress_free_compressor(void *_c)
+{
+ struct xpress_compressor *c = _c;
+
+ if (c) {
+ lz_mf_free(c->mf);
+ FREE(c->cached_matches);
+ FREE(c->optimum);
+ FREE(c->chosen_items);
+ FREE(c);
+ }
+}
+
+const struct compressor_ops xpress_compressor_ops = {
+ .get_needed_memory = xpress_get_needed_memory,
+ .create_compressor = xpress_create_compressor,
+ .compress = xpress_compress,
+ .free_compressor = xpress_free_compressor,
+};
git://wimlib.net / wimlib / blobdiff